There is a company here that boasts an R value of 10. How is that possible when that translates to a U-Value of .10? I understand that it is triple pane with a foam core frame, but even so, all data I've seen on similar products goes to (lowest) a .20 or there abouts. Maybe even a .18 is beleivable, but a .10? Any help here would be appreciated.

They are probably citing the CENTER OF GLASS as R-10. The lowest U-value that you mentioned of .20 to .18 is presumably the honest, OVERALL TOTAL UNIT U-value. If a window has a total unit U-value of let's say .18 (about as low as it goes), the corresponding center of glass could possibly be close to R-10 but the overall R-value would usually be in the upper 4s. People should not fool with mother nature, spit into the wind, tug on Superman's cape, or mix their center-of-glass and total unit R and U values!

When window salesman start talking about the R-values, that's usually a good time to look in the yellow pages for someone else. Besides the points that tru_blue mentions, they could also be referring to a foam-filled frame, which "hypothetically" would be R-10 or more. But since 90% of the window is glass, the overall energy efficiency of the window is a bigger concern.

My advice to people I talk to is to ignore talk about r-values when dealing with windows and rely soley on the NFRC u-value ratings. The NFRC ratings may not be perfect, but at least they seem to compare glass fairly.

I agree 100%. Some sales people just don't see the logic of those statements and insist on using R values for windows when we all know R values for windows stinks... a wall being R 30 and a window being R 3?? Not that impressive. Stick to the industry standards and the consumer becomes more educated rather than confused.

We have a lot to be thankful for with this tax credit. It has really awakened the window industry and forced innovation where things have been rather stagnant for a while. We're seeing new glazings, spacers, extrusions at a rate that we haven't seen in many years.

The central issue that keeps coming back in my mind is that we're putting R-4 to R-8 windows into walls that are R-11 to R-15. That leaves a lot of room for improvement. That means a bright future for us as technology increases, and the price of that technology grows more affordable.

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